To see if your adapter is working, disconnect it from the STB and short the TX and RX pins on the adapter itself. Use a terminal program like PuTTY or Tera Term. If what you type is echoed back, your adapter and drivers are functioning correctly. Hardware Reset Timing
If you want, tell me the device model and what you’ve already tried and I’ll give device-specific steps. Bootrom Error Wait For Get Please Check Stb Uart Receive
If you have confirmed hardware and software are correct but still see the error, your device has deeper issues. To see if your adapter is working, disconnect